#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
struct node
{
	int x;
	int y;
}pack[1100];
bool cmp(node a,node b)
{
	if(a.y!=b.y) return a.y<b.y;
	else return a.x<b.x;
}
int main()
{
	int t;
	scanf("%d",&t);
	while(t--)
	{
		int n;
		char s[1100];
		int cnt = 0;
		int flag = 0;
		scanf("%d",&n);
		for(int i = 0;i<n;i++)
		{
			scanf("%d %d",&pack[i].x,&pack[i].y);
		}
		sort(pack,pack+n,cmp);
		for(int i = 0;i<n;i++)
		{
			if(!i)
			{
				for(int j = 0;j<pack[i].x;j++)
				{
					s[cnt++] = 'R';
				}
				for(int j = 0;j<pack[i].y;j++)
				{
					s[cnt++] = 'U';
				}
			}
			else 
			{
				if(pack[i-1].x>pack[i].x)
				{
					flag = 1;
					break;
				}
				for(int j = pack[i-1].x;j<pack[i].x;j++)
				{
					s[cnt++] = 'R';
				}
				for(int j = pack[i-1].y;j<pack[i].y;j++)
				{
					s[cnt++] = 'U';
				}
			}
		}
		if(!flag)
		{
			printf("YES\n");
			s[cnt]='\0';
			puts(s);
		}
		else printf("NO\n");
	}
}
